The present invention relates to the battery switches on motor vehicles, particulary trucks used to transport dangerous materials.
The state of the art in this field is particularly illustrated by French Patent No. 2,562,322 in the name of the applicant. In this prior device, an electromagnetic switch with pull and hold coils is mounted under a sealed cover with the control electronics enabling remote control by means of electrical lines carrying a very low current. The movable armature of the electromagnetic device carries the single- or multi-pole main contact parts of the battery circuit. The armature also carries an auxiliary delayed action contact which, during the opening of the main circuit, provides either precontact of the alternator excitation circuit with ground, in the case of an alternator with a built-in regulator, or pre-cutoff of the alternator excitation circuit, in the case of an alternator with an external regulator. However, this mechanically obtained delay is inaccurate and difficult to adjust. The adjustment problems can be detrimental to the excitation diodes of the alternator.
In addition, the auxiliary pre-contact or pre-cutoff contact normally made to switch off a low intensity current risks being destroyed by electrical arcing in the case in which the user, after having closed the control contact, opens it and closes it again within a short period of time, for example, as a result of starting difficulties.
Another operational fault can arise due to a momentarily large voltage drop at the battery. This causes the untimely tripping of the electromagnetic switch and thus prevents the functioning of the vehicle.